Synthesis and study of triphenylphosphines functionalized at the 4-positions through the nitrogen atoms in 1,4,7,10-tetraoxa-13-azacyclopentadecane and the X-ray structure of the oxide of the molecule substituted at all three positions

Hybrid phosphine crown ether ligands have been obtained from PhP(OMe)(2) an d P(OPh)(3) and carbanions generated by low-temperature Li/Br exchange reac tions involving 4'-bromo-N-phenylaza-15-crown-5 and n-butyllithium. The A(1 ) nu (CO) values for the Ni(CO)(3)L complexes of these phosphines have been found to be 2063.7 and 2060.8 cm(-)1, for the bis (Ib) and tris (Ic) crown species, respectively, indicating the significant electron-donating abilit ies of the nitrogen atoms. Addition of NaSCN salts in dichloromethane cause s these frequencies to increase by 2.40 (Ib) and 3.70 cm(-1) (Ic), indicati ng that the P(III) centers detect the presence of crown-coordinated ions. T he oxide of Ic has been prepared and the X-ray structure obtained. A promin ent feature of that structure, R (3) over bar symmetry, is that the nitroge n atoms are nearly planar and the ring carbon-to-nitrogen distances are 1.3 75 Angstrom, features that are also consistent with a significant amount of sp(2) C-N double-bond character. The phenyl rings are arranged in a typica l propeller shape with torsion angles of 132.4 degrees.